AR Revolution on Construction Sites for Civil Engineering Construction Managers: Preventing Construction Errors with LRTK

The "Invisible Risks" Civil Construction Management Engineers Face on Site

As a civil construction management engineer entrusted with construction sites every day, do you constantly feel the risk that slight discrepancies between drawings and the actually constructed works could later develop into major problems? On site, even when things appear to be constructed correctly at first glance, mistakes such as "the foundation was off by a few centimeters (a few in)" or "the finished elevation doesn't match the design" can be discovered during final inspections or as-built measurements. These invisible risks are difficult to detect in the moment and later cause rework or repairs, leading to unnecessary costs and schedule delays. Even for skilled craftsmen, tiny errors that human visual judgment alone cannot completely eliminate can hide, and construction managers must always work alongside that anxiety.

Furthermore, in recent years, due to labor shortages and an increase in younger engineers, many staff with limited site experience are now present. Areas that could previously be covered by the instincts and experience of veterans tend to be overlooked on sites lacking experience. To reduce human errors on site to nearly zero, it can be said that relying solely on human intuition has reached its limits.

The Main Cause of Construction Errors: Site Operations Relying on Visuals and Sensation

On civil engineering sites, there are still many situations where confirmations are made by visual inspection using analog methods such as tape measures, levels, and chalk for layout. Judgements based on intuition—such as "this should be fine" or "the drawing shows it here, so the position is probably correct"—have become a primary cause of construction errors. For example, work may continue after a small measurement error in foundation layout, or excavation depth may rely on visual estimation and later be found to be off by several centimeters (several in) when surveyed.

With traditional methods, surveyors or site supervisors would use transits or levels to check at key points, but it is difficult to manage every single step of construction with high-precision surveying at all times, and much is left to the eyes and experience of the craftsmen. Therefore, complex processes involving multiple stages and work in hard-to-see locations tend to be breeding grounds for mistakes. To reduce situations of "it looks right, but actually was displaced," an update to site operations themselves is necessary.

Visualization with AR: Grasp Design-to-Reality Discrepancies on the Spot

In response to these on-site risks, attention has recently focused on the use of AR (augmented reality) technology. By using AR that overlays design drawings or 3D design models onto the real-world site through a smartphone or tablet camera, you can visualize slight discrepancies between design and reality on the spot. For example, if you display a 3D model of the planned finished structure in AR over a structure under construction, you can instantly check the finished shape at a glance and immediately notice if it deviates from the planned line.

At rebar placement sites, overlaying the placement drawings on AR allows real-time detection of errors in the number of bars or spacing. For buried object location confirmation, AR can display underground structures—difficult to grasp from drawings alone—as translucent overlays, reducing the risk of excavating the wrong location. In practice, there are reports that overlaying design drawings with the site during construction enabled early detection and correction of construction defects, greatly reducing rework and material waste. AR-based site visualization has become a powerful ally in preventing human error.

Centimeter-Level Position Management Using High-Precision GNSS (LRTK)

However, to fully utilize AR on site, accurate position awareness is indispensable. Ordinary smartphone GPS has errors on the order of several meters (several ft), which does not meet the precision required for civil engineering work. Enter high-precision positioning technology known as RTK-GNSS (real-time kinematic GNSS). In particular, LRTK is a solution that makes RTK-GNSS easy to use on smartphones and tablets: by attaching a dedicated small antenna to the device and receiving correction information, it achieves positioning accuracy that is always within a few centimeters (a few in).

The greatest advantage of using high-precision GNSS is that it can automate the alignment between design data and real space. Traditionally, after arriving on site, equipment would be set up to match drawing reference points, and only after staking or chalk marking would coordinates be aligned. However, with systems like LRTK, simply holding up a smartphone on site will project the design model into the correct position based on global coordinates. Without tedious initial calibration work, you can always display AR without misalignment.

Furthermore, centimeter-level positioning (inch-level positioning) provided by LRTK ensures that the model remains firmly fixed in space even as the user walks around, giving the advantage that AR displays remain stable and do not jitter. Even when moving across large civil sites, the AR model will not slide or float but will be displayed perfectly aligned with the real object, allowing you to confidently use it for position confirmation and surveying tasks. High-precision GNSS becomes the eyes of AR, spreading accuracy control throughout the site.

Changes in As-Built Management: Instantly Confirm Cross-Sections, Volumes, and Errors

The combination of AR and GNSS is also set to greatly change as-built management—the process of confirming that completed structures match the design shape and dimensions. Traditionally, after construction completion a survey team would take cross-sections on site to check heights or prepare as-built tables for client inspections. With AR, you can check cross-sectional shapes and finished heights on the spot during construction. For example, in embankment compaction for roads, projecting the design cross-section line in AR and overlaying it on the actual embankment allows real-time visual identification of under- or over-fill.

Also, by combining the LiDAR scanner or photogrammetry functions built into smartphones or tablets with LRTK, you can acquire 3D point cloud data of the work area in a short time and immediately perform volume calculations and as-built error checks. Previously, earthwork quantity calculations and as-built evaluations took time and there was a lag before report creation, but if measurement and visualization can be completed on site, you can decide there and then whether additional fill is needed or if too much has been excavated.

The Ministry of Land, Infrastructure, Transport and Tourism is also promoting efforts under "i-Construction 2.0" to visualize as-built management and streamline inspections by projecting 3D data acquired on site in AR [国土交通省 i-Construction 2.0 動向](https://tech.siliconstudio.co.jp/column/contents49/#3). Going forward, the style of checking and sharing as-built information on tablets rather than relying on paper tables will likely become standardized. With AR and high-precision positioning, as-built management will be visualized in real time, and site supervisors, craftsmen, and clients will be able to share the same information instantly.

Complete with a Single Smartphone: Implementation Steps and Operational Examples of AR × LRTK

So how do you actually use AR and LRTK on site? The barrier is surprisingly low, and it can be done with the convenience of "complete with a single smartphone." The general introduction flow is as follows:

• Prepare design data: First, prepare the 3D design models or drawing data for the work (BIM/CIM models or CAD data) and upload them to a dedicated cloud or app. Converting drawings to 3D in advance makes AR display on site easier.

• Set up equipment: On site, attach a small GNSS antenna for LRTK to a smartphone or tablet and launch the app. Antennas are lightweight and typically attachable to helmets or devices. Then connect to GNSS correction information (VRS or satellite reference station networks) to enable centimeter-level accuracy (half-inch accuracy).

• AR display and positioning: Select the relevant design model in the app and start the composite display with the camera feed. Because the device's position coordinates are corrected with high precision by LRTK, the design model will be displayed perfectly over the actual construction location without special marker placement or manual adjustment.

• On-site use: Then simply look at the device screen to confirm virtual lines or structure models drawn on the ground. For example, in slope work the design gradient line is displayed on the slope in AR, allowing operators to use it as a reference for excavating or filling with machinery. In foundation work, virtual piles (pins) can be displayed in AR at the design positions, enabling layout work to be completed without physically driving piles. Since target points can be instructed from a safe distance, marking work in hazardous locations is unnecessary.

As operational examples, sites have visualized road centerlines and curb lines to ensure construction accuracy, and displayed pier placement positions in AR beforehand to share with heavy equipment operators for smooth installation. With smartphones and AR, everyone on site can proceed with the same image of the finished product, reducing misreading of drawings and communication errors. There is no need to carry special professional equipment, and the convenience of "one person can perform surveying through as-built confirmation" is transforming site operations.

AR Management Raises Trust with Clients

Introducing AR and LRTK contributes not only to improved efficiency and accuracy within the site but also to strengthening trust with clients (owners). For construction managers, proving at client inspections that work has been completed according to the design is important, and AR makes that proof extremely smooth. For example, showing a tablet screen with an overlay of the completed model and the as-built will make construction accuracy immediately understandable. Points that were difficult to convey with words or drawings can be explained visually, greatly increasing client confidence.

AR is also effective for communication with clients and supervisory staff during construction. Presenting images in meetings that composite photos of the site with the model or performing on-site confirmations with AR as needed allows you to immediately answer questions such as "why is this process necessary?" or "how will the finished product look?" As a result, information sharing between contractor and client becomes denser and the overall project reliability improves. At explanatory meetings for local residents, projecting the projected completion drawing to scale on site is expected to make it easier to obtain understanding and cooperation from residents.

Sites where quality and progress are always visualized are transparent and reassuring even to third parties. Actively taking measures to prevent mistakes enhances corporate credibility itself and contributes to improved evaluations for contractors.

Looking Ahead to Future Site Standards: Tools Needed for Construction Management

As ICT and DX advance, what tools should become standard on future civil construction management sites? While the Ministry of Land, Infrastructure, Transport and Tourism’s i-Construction initiative introduces various advanced technologies such as drone surveying and machine-guided heavy equipment, from the construction management perspective the tools to watch are those combining high-precision GNSS and AR. This will bring an era where construction managers who used to run around sites with paper drawings and tape measures will be able to perform surveying and management with a single tablet.

Specifically, the following items can be considered site-standard tools:

• High-precision positioning equipment: RTK-capable GNSS receivers and electronic reference plates that can perform centimeter-level positioning and surveying.

• AR-capable viewers: Smartphone/tablet apps that can overlay BIM/CIM models and drawings on site.

• 3D scanners: Laser scanners and photogrammetry tools that can quickly acquire as-built point cloud data (recently, built-in smartphone LiDAR can be used as a substitute).

• Cloud collaboration platforms: Services that enable real-time sharing of 3D data and site information between site, office, and clients.

By combining these, site supervisors can complete measurement, confirmation, and reporting on the spot without requesting surveyors. Especially on small regional sites or sites with limited personnel, using digital tools to manage efficiently with a small team is required. Younger engineers tend to have high affinity for digital devices, and mastering these tools will help bridge generational gaps in skill transfer. What future construction managers need is flexibility to combine experiential knowledge with the latest technology.

LRTK as an Option: Solo As-Built and Position Management

Finally, as one concrete solution to realize the AR and high-precision positioning described above on site, we introduce LRTK. LRTK is an AR-compatible RTK-GNSS system provided by Refixia Co., and is characterized by the ease of use—simply attaching an antenna to devices such as iPhones or iPads. It is designed so that anyone can intuitively use AR technology without the need for on-site alignment tasks.

By using LRTK, surveying tasks that used to require two people and layout work that relied on veteran intuition can be completed by a single person. For example, from reference point surveying to as-built measurement and even photo documentation, a single smartphone can handle everything, promising significant reductions in work time and labor costs. For civil construction management engineers, LRTK can be described as a new kind of on-site "ruler."

Major construction companies and regional small-to-medium contractors alike have already begun introducing LRTK as part of site DX. The style of "one person, one smartphone from surveying to AR" is expected to be a trump card for labor saving and productivity improvement in the construction industry facing population decline. Looking ahead to future site standards, consider adding simple surveying with LRTK to your options for preventing construction errors and improving efficiency. Start a step that will bring an AR revolution to your site and add new value and peace of mind to construction management. The day when the fusion of seasoned intuition and cutting-edge technology becomes the new norm in construction management is not far off.